Patent DE-102009037946-A1 (DE)
Title: Utilization of the wastewater occurring during the production of lignocellulosic fibers, comprises combusting the parts of the substances contained in the wastewater or recovering the parts of the substances as usable substances
Inventor: PAASCH VOLKER
IPC: C02F9/06
Filed: 2009-08-18
Abstract: The method for the utilization of the wastewater (4) occurring during the production of lignocellulosic fibers, comprises combusting the parts of the substances contained in the wastewater or recovering the parts of the substances as usable substances or combusting the parts of the substances contained in the wastewater or recovering the other parts of the substances as usable substances, initially subjecting the wastewater to an electrochemical treatment (6) for the separation of cations contained in the wastewater, and separating high-molecular substances (10) from low-molecular substances. The method for the utilization of the wastewater (4) occurring during the production of lignocellulosic fibers, comprises combusting the parts of the substances contained in the wastewater or recovering the parts of the substances as usable substances or combusting the parts of the substances contained in the wastewater or recovering the other parts of the substances as usable substances, initially subjecting the wastewater to an electrochemical treatment (6) for the separation of cations contained in the wastewater, and separating high-molecular substances (10) from low-molecular substances in a fractionation process (9), where a concentrate (7) enriched with the cations is processed in the fractionation process. The wastewater is initially treated in the fractionation process. The fraction enriched with the high-molecular substances is fed to the electrochemical treatment. The wastewater contains lignosulfonate on the basis of sodium, magnesium, calcium or ammonium. The parts of the high-molecular substances are lignin sulfonic acid, are combusted and are converted to a usable substance. The low-molecular substances consist of sulfuric acid and organic components such as sugar, fatty acids and/or lignin fragments, and are fed to a biological anaerobic treatment, where the gases developed during the wastewater treatment are fed to a combustor. The filtrate of the wastewater treatment is desulfurized and is again used as return water. The sulfur removed from the filtrate of the wastewater treatment is fed to the same combustor, in which the gases developed during the wastewater treatment and the high-molecular substances are combusted. The sulfur compounds such as sulfur dioxide contained in the exhaust gases of the combustor are converted to sulfuric acid or ionized bisulfite (HSO 3->) or ionized sulfate (SO 32>->)-containing solution by reacting with water or alkali solutions such as sodium sulfite, sodium hydrosulfite or sodium hydroxide. The sulfuric acid or ionized bisulfite or ionized sulfate-containing solution are used as receiving solution during the electrochemical treatment to receive cations of the base that is used in the fiber material production from the wastewater, where the cations are sodium ions, magnesium ions, calcium ions or ammonium ions. The wastewater is guided to reaction chambers lying in between ion-selective walls for electrochemical treatment and is flowed-through by electric current, where a flow of the received ions to the wastewater or a flow of ions delivered from the wastewater is produced through the ion-selective walls. The walls are permeable only for the cations and are partially permeable for the anions, where bipolar membranes are partially used as walls. The flow of the ions received from the wastewater consists of positive hydrogen ions and the flow of ions delivered from the wastewater consists of positive sodium-, magnesium-, calcium- or ammonium ions. The sulfuric acid or ionized bisulfite or ionized sulfate-containing solution is guided to a further reaction chamber with walls partially permeable for ions and is flowed-through by electric current. The inflow of ions of the base in the receiving solution and an outflow of the hydrogen ions from the receiving solution to the wastewater guided into an adjacent reaction chamber are produced through the walls. A rinsing liquid is guided into the further reaction chamber with sodium sulfate of the base used in the fiber material production, where the further reaction chamber has an anode forming hydrogen ions and a wall partially permeable for ions. The rinsing liquid is flowed-through by electric current. The outflow of the cations of the base to the receiving solution guided into the adjacent reaction chamber is produced through the wall partially permeable for ions. The parts of the receiving solution are converted into hydrogen sulfate through the inflow of the protons and the outflow of the cations of the base. The hydrogen sulfate is fed into a modified rinsing liquid of the further reaction chamber, which has hydrogen-ion forming cathode and wall partially permeable for ions. The inflow of cations of the base to the modified rinsing liquid guided into the reaction chamber is produced through the wall partially permeable for ions. The hydrogen sulfate is again deprotonatedly converted into a sulfate through the inflow of the cations of the base and the hydrogen-ions. The electrochemical treatment is carried out, so that 80% of cations contained in the guided wastewater are removed from the wastewater. The fractionation process is carried out, so that the carboxylic styrene-butadiene load in the fraction containing the high-molecular substances amounts to more than 80% of the carboxylic styrene-butadiene load in the wastewater guided to the fractionation process.